This invention relates to a method of melting a metal, particularly to the method which is suitable for melting iron scraps having a high melting point
While melting of metals, particularly iron scraps, is generally achieved by utilizing arcing in an electric furnace, the iron scraps melt nonuniformly and so-called cold spots are liable to occur according to this method. Accordingly, it is also practiced to employ an oxygen-assisted fuel burner in combination with the electric furnace.
Meanwhile, the oxygen injection method is also employed in order to promote productivity and melting speed. In this method, a micropowdery coal and coke are injected together with oxygen into the melt remaining in the furnace to effect an oxidation reaction whereby to melt the scraps by the heat of reaction.
However, the first method of melting a metal using an electric furnace described above involves a disadvantage that cold spots are inevitably left in the metal and that it must resort to the electric power as the source of energy, although it has an advantage that it can readily yield a high temperature and allows easy temperature adjustment. Meanwhile, in the second method in which an oxygen-assisted fuel burner is used in addition to the electric furnace, 60 to 80% of the total energy resorts to the electric power, and besides it is well known that the energy efficiency of the electric power is only about 20 to 25%, when generating efficiency, melting efficiency, etc. are all taken into consideration. In addition, referring to the generation of CO.sub.2 which is notorious as a causative of global environmental disruption, it is reported that about 150 m.sup.3 of CO.sub.2 is generated for melting 1 ton of metal scraps utilizing the electric power generated by use of heavy oils, so that a countermeasure therefor must be taken.
In the oxygen injection method, the above problems can be cleared since no electric power is employed. However, in this method, oxygen, a micropowdery coal and coke are injected to the melt to carry out an oxidation reaction and effect melting of the metal, so that a portion of the melt must constantly be allowed to remain in the melting furnace. This may cause no problem when the melting operation is carried out continuously, but inevitably yields poor productivity in the case of a batchwise melting operation or of intermittent melting operation, since the melt cannot entirely be removed from the melting furnace.
Meanwhile, the fuel is usually burned at an oxygen-to-fuel ratio of from 1.0 to 1.5 in the oxygen-assisted fuel burner, and use of such type of burner for melting iron scraps causes reduction in the yield due to oxidation of the scraps and the like to be caused by the excess amount of oxygen, leading to a metal loss. In addition, this burner further involves a disadvantage that the recarburizer is also burned based on the same reason and that NO.sub.x are generated in large amounts.